The family of a Minneapolis man who is awaiting trial on terrorism conspiracy charges say they have been prevented from visiting him in prison, where he remains in 23-hour-a-day solitary confinement with little access to the outside world.

Fadumo Hussein said that she was repeatedly turned away when she tried to visit her son, Guled Omar, who has been shuttled between several area jails since his arrest last April on federal charges of conspiring with others to join the Islamic State of Iraq and the Levant (ISIL).

Hussein said her son told her in a brief phone conversation earlier this week that he was living under harsh conditions in the Ramsey County jail and that he was suffering from several ailments because his cell was kept so cold.

Authorities insist that Omar, 21, has been segregated from other prisoners for his protection, but declined to comment on why his co-defendants in the case have been moved to the general population in other jails.

The last time she tried to see him, Hussein says, she and her daughter were pulled out of line as they entered the jail and told that they would not be let in, without further explanation. With no other way of contacting him, the family racked up a $300 phone bill last month accepting calls from Omar, they said.

"If this continues, he will suffer mentally," Hussein said Thursday, through an interpreter. "This confinement is inhumane and the way they're treating him, it's something that's beyond punishment."

Family members say that Omar is allowed out of his cell only one hour a day to shower or video chat with relatives, which prompted his attorney to write two letters to U.S. District Judge Michael Davis, who is presiding over the case, asking that his client be transferred back to Anoka County jail.

"He does not have access to a canteen to purchase food or toiletries nor is he allowed to use vending machines," the attorney, Glenn Bruder, wrote in a Sept. 14 letter to Davis. "Omar appeared depressed and states that he 'doesn't know how [he] can make it five months in these conditions.' " His trial is scheduled for mid-February.

Furthermore, Bruder wrote, restrictions on the amount of time he was allowed to visit with Omar has limited his ability to prepare a defense in time for trial.

The U.S. Marshals Service, which oversees his detainment, said Omar was isolated because authorities believed he would have a "target on his back" because of the seriousness of the charges against him. The agency said that the decision came at the FBI's request.

Kyle Loven, a spokesman for the FBI's Minneapolis field office, declined to comment on the matter, referring questions back to the U.S. Marshals Service.

Bruder pointed out that Judge Davis had ordered several of the defendants moved to less restrictive confinement when the issue came up at a May 12 hearing.

Prosecutors contend that Omar was part of a year-old conspiracy of at least a dozen men who sought to aid ISIL in its fight to carve out an Islamic-run state. Several local men managed to slip out of the country and join ISIL fighters in Syria and Iraq, authorities said, with some dying in the fighting there.

Federal authorities this week filed a broader indictment, which brought additional charges against some or all of the defendants, including perjury, financial aid fraud and conspiracy to commit murder abroad. The latter charge carries a maximum sentence of life in prison.

Several defense attorneys and families of the remaining defendants accused the government of dangling the possibility of a life sentence over the men to pressure them into pleading guilty.

"It was troubling to me to hear that those who didn't take the plea deal are facing more charges and it seems like they're being punished for not taking the plea deal," said Teresa Nelson, legal director for the local chapter of the American Civil Liberties Union.

She said that while it wasn't unusual for authorities to place defendants in solitary confinement "as a way of preventing him from communicating with the outside world," a growing body of research points to the devastating effects of solitary confinement on prisoners' mental health.

Hussein, Omar's mother, said that it was unclear why authorities were singling out her son.

"My child never stole anything, he did not kill anybody, he did not rape anybody, he did not burglarize any place," she said Thursday. "How can it be possible that he could be looking at spending the rest of his life in jail?"

Drawing early scrutiny

A federal search warrant application filed earlier this year suggested that authorities first took an interest in Omar three years ago.

In the filing, authorities argued that Omar, whose older brother, Ahmed Ali Omar, was one of at least 22 local men who left the state nearly a decade ago to join Al-Shabab, previously tried to join Al-Qaida's branch in Somalia but was stopped by authorities at the airport.

The search warrant also said that, in addition to his public Twitter account, he maintained a "dirty jihadi" account that he hid from all but his closest friends and used to communicate with ISIL sympathizers from around the world.

Omar's attorney declined to comment on the allegations.

"I'd prefer to try the case to the jury rather than speculate about what the government may or may not present at trial," he said, adding that the new charges didn't justify his client's continued isolation.

"It's not unusual if you're John Gotti sitting in a federal max prison," Bruder said. "I've never seen a pretrial detaining in 30 years of practicing law."